<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 100px;
            height: 100px;
        }
        
        .red {
            background-color: red;
        }
        
        .green {
            background-color: green;
        }
    </style>
</head>

<body>
    <div class="box red"></div>
    <div class="box green"></div>
    <div class="box red"></div>
</body>

</html>